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Robot reveals when tetrapods first walked tall

Scientists reverse engineer a bot to learn about the first land animals. Nick Carne reports.

Tetrapods learnt to walk efficiently on land earlier than previously thought, a new study suggests, and the prehistoric walking style of those four-legged vertebrates probably looked at least a little like this video.

European researchers have “reverse engineered” Orobates pabsti, a large, plant-eating animal, to create a robotic simulation of how it likely moved around the Earth some 290 million years ago. It has been dubbed the OroBOT.

Fossil remains of Orobates have been matched to corresponding preserved tracks, revealing insights into its movement and gait.

By combining these two inputs with measurements of four living amphibian and reptile species – salamanders, skinks, iguanas and caimans – a team led by John Nyakatura of the Humboldt Universität zu Berlin, Germany, created a digital reconstruction and the robotic simulation, which they then used to explore the plausibility and effectiveness of potential walking styles.

They suggest, as a result, that Orobates was probably capable of a more upright walking gait than has typically been associated with very early tetrapods, and that the development of efficient locomotion on land preceded the evolution and diversification of reptiles, birds, and mammals.

It was the approach, as much as the results, that was impressive. Nyakatura and colleagues believe they are the first to use multiple quantitative methods in such a study, with the aim of covering as many bases as possible.

Studies that focus solely on fossil anatomy, they say, may permit a range of motion at joints that is much larger than that used during locomotion, and also may neglect the biomechanics of the whole organism.

At the same time, relying primarily on mechanical modelling and engineering may neglect anatomical detail, while studying fossil trackways in isolation leads to uncertainty as different movements or gaits can produce nearly identical trackways.

In their project they used the dynamic OroBOT simulation to quantify the physics of locomotion, by assessing mechanical power expenditure, the ability to walk without excessive tilting, ground reaction forces and the precision of the match with the fossil trackway, then the physical OroBOT to validate the results of the dynamic simulation under real-world conditions.

“Our quantitative reconstruction of the locomotion of Orobates is consistent with previous qualitative locomotor postulations based on fossil trackways, and was found here to be relatively erect (within the spectrum of sprawling locomotion), balanced and mechanically power-saving,” they write.

“More-erect limb postures are linked with a greater capacity for speed, reduced torsional stresses at limb long-bone midshafts, and reduced power use to accelerate the body in the direction of travel. The locomotion of Orobates was advanced – according to the metrics studied here – in comparison to earlier tetra-pods.”